Micromechanical devices are small structures typically fabricated on a semiconductor wafer using techniques such as optical lithography, metal sputtering, oxide deposition, and etching that have been developed for the fabrication of integrated circuits. Digital micromirror devices (DMDs), sometimes referred to as deformable mirror devices, are a type of micromechanical device. Digital micromirror devices can be used in a variety of applications such as optical display systems or optical switching systems.
DMD arrays have many advantages when used in optical switching systems. Specifically, a DMD array has the ability to selectively reflect portions of a light beam that is directed onto its surface. This feature can be used to implement a variety of functions such as signal monitoring, or wavelength-based switching. U.S. Pat. No. 6,295,154 entitled “Optical Switching Apparatus,” which is hereby incorporated by reference, describes the use of DMD arrays for these kinds of optical switching applications. The present application describes the use of lenses, polarizers, mirrors, and other such components to interface a free-space-operating DMD array with a waveguide-based optical system. One example of a set of optical interface equipment employed in a DMD array is disclosed in U.S. Pat. No. 6,398,389 entitled “Solid State Light Source Augmentation for SLM Display Systems,” which is also hereby incorporated by reference.
There are several difficulties that may be associated with the use of lenses, polarizers, mirrors and other such components in a free-space optical system. First, the optical components are often physically and manually aligned for optimal performance. Second, the operation of a free-space optical system employing such components can be affected by movement, vibration, or mechanical stress. Third, free-space optical systems may be relatively large in size compared to other types of optical systems. Fourth, given their relatively large size, free-space optical systems may be especially susceptible to thermal stresses; in particular, if one portion of the system is heated to a greater extent than the rest of the system, this can affect the alignment and performance of the entire system.